This patch adds support that enables passing of file descriptors
to the QEMU monitor where they will be stored in specified file
descriptor sets.
A file descriptor set can be used by a client like libvirt to
store file descriptors for the same file. This allows the
client to open a file with different access modes (O_RDWR,
O_WRONLY, O_RDONLY) and add/remove the passed fds to/from an fd
set as needed. This will allow QEMU to (in a later patch in this
series) "open" and "reopen" the same file by dup()ing the fd in
the fd set that corresponds to the file, where the fd has the
matching access mode flag that QEMU requests.
The new QMP commands are:
add-fd: Add a file descriptor to an fd set
remove-fd: Remove a file descriptor from an fd set
query-fdsets: Return information describing all fd sets
Note: These commands are not compatible with the existing getfd
and closefd QMP commands.
Signed-off-by: Corey Bryant <address@hidden>
---
v5:
-This patch is new in v5 and replaces the pass-fd QMP command
from v4.
-By grouping fds in fd sets, we ease managability with an fd
set per file, addressing concerns raised in v4 about handling
"reopens" and preventing fd leakage. (address@hidden,
address@hidden, address@hidden)
v6
-Make @fd optional for remove-fd (address@hidden)
-Make @fdset-id optional for add-fd (address@hidden)
v7:
-Share fd sets among all monitor connections (address@hidden)
-Added mon_refcount to keep track of monitor connection count.
v8:
-Add opaque string to add-fd/query-fdsets.
(address@hidden)
-Use camel case for structures. (address@hidden)
-Don't return in-use and refcount from query-fdsets.
(address@hidden)
-Don't return removed fd's from query-fdsets.
(address@hidden)
-Use fdset-id rather than fdset_id. (address@hidden)
-Fix fd leak in qmp_add_fd(). (address@hidden)
-Update QMP errors. (address@hidden, address@hidden)
monitor.c | 188 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
qapi-schema.json | 98 ++++++++++++++++++++++++++++
qmp-commands.hx | 117 +++++++++++++++++++++++++++++++++
3 files changed, 403 insertions(+)
diff --git a/monitor.c b/monitor.c
index 49dccfe..f9a0577 100644
--- a/monitor.c
+++ b/monitor.c
@@ -140,6 +140,24 @@ struct mon_fd_t {
QLIST_ENTRY(mon_fd_t) next;
};
+/* file descriptor associated with a file descriptor set */
+typedef struct MonFdsetFd MonFdsetFd;
+struct MonFdsetFd {
+ int fd;
+ bool removed;
+ char *opaque;
+ QLIST_ENTRY(MonFdsetFd) next;
+};
+
+/* file descriptor set containing fds passed via SCM_RIGHTS */
+typedef struct MonFdset MonFdset;
+struct MonFdset {
+ int64_t id;
+ int refcount;
+ QLIST_HEAD(, MonFdsetFd) fds;
+ QLIST_ENTRY(MonFdset) next;
+};
+
typedef struct MonitorControl {
QObject *id;
JSONMessageParser parser;
@@ -211,6 +229,8 @@ static inline int mon_print_count_get(const Monitor *mon) {
return 0; }
#define QMP_ACCEPT_UNKNOWNS 1
static QLIST_HEAD(mon_list, Monitor) mon_list;
+static QLIST_HEAD(mon_fdsets, MonFdset) mon_fdsets;
+static int mon_refcount;